MIC2007YML datasheet(21/30 Pages) MICREL

21 / 30 page

Micrel, Inc.

MIC20xx Family

August 2011

M9999-080211-D

Functional Description

VIN and VOUT

VIN is both the power supply connection for the internal

circuitry driving the switch and the input (Source

connection) of the power MOSFET switch. VOUT is the

Drain connection of the power MOSFET and supplies

power to the load. In a typical circuit, current flows from

VIN to VOUT toward the load. Since the switch is bi-

directional when enabled, if VOUT is greater than VIN,

current will flow from VOUT to VIN.

When the switch is disabled, current will not flow to the

load, except for a small unavoidable leakage current of

a few microamps. However, should VOUT exceed VIN by

more than a diode drop (~0.6 V), while the switch is

disabled, current will flow from output to input via the

power MOSFET’s body diode.

If discharging CLOAD is required by your application,

consider using MIC20X4 or MIC20X7; these MIC20XX

family members are equipped with a discharge FET to

insure complete discharge of CLOAD.

Current Sensing and Limiting

MIC20XX protects the system power supply and load

from damage by continuously monitoring current

through the on-chip power MOSFET. Load current is

monitored by means of a current mirror in parallel with

the power MOSFET switch. Current limiting is invoked

when the load exceeds the set over-current threshold.

When current limiting is activated the output current is

constrained to the limit value, and remains at this level

until either the load/fault is removed, the load’s current

requirement drops below the limiting value, or the

switch goes into thermal shutdown.

Kickstart™

2003

2004

2005X

2006

2007

2008

2009X

2013

2014

2015

2016

2017

2018

2019X

Only parts in bold have Kickstart™.

(Not available in 5-pin SOT-23 packages)

The MIC201X is designed to allow momentary current

surges (Kickstart™) before the onset of current limiting,

which permits dynamic loads, such as small disk drives

or portable printers to draw the energy needed to

overcome inertial loads without sacrificing system

safety. In this respect, the Kickstart™ parts (MIC201X)

differs markedly from the non-Kickstart™ parts

(MIC200X) which immediately limit load current,

potentially starving the motor and causing the appliance

to stall or stutter.

During this delay period, typically 128ms, a secondary

current limit is in effect. If the load demands a current in

excess the secondary limit, MIC201X acts immediately

to restrict output current to the secondary limit for the

duration of the Kickstart™ period. After this time the

MIC201X reverts to its normal current limit. An example

of Kickstart™ operation is shown in Figure 3.

Figure 3. Kickstart™ Operation

Figure 3 Label Key:

A. MIC201X is enabled into an excessive load (slew

rate limiting not visible at this time scale) The initial

current surge is limited by either the overall circuit

resistance and power supply compliance, or the

secondary current limit, whichever is less.

B. RON of the power FET increases due to internal

heating (effect exaggerated for emphasis).

C. Kickstart™ period.

D. Current limiting initiated. FAULT/ goes LOW.

E. VOUT is non-zero (load is heavy, but not a dead short

where VOUT = 0V. Limiting response will be the same

for dead shorts).

F. Thermal shutdown followed by thermal cycling.

G. Excessive load released, normal load remains.

MIC201X drops out of current limiting.

H. FAULT/ delay period followed by FAULT/ going

HIGH.

Undervoltage Lock-Out

Undervoltage lock-out insures no anomalous operation

occurs before the device’s minimum input voltage of

UVLOTHRESHOLD which is 2V minimum, 2.25V typical,

and 2.5V maximum had been achieved. Prior to

reaching this voltage, the output switch (power

MOSFET) is OFF and no circuit functions, such as

FAULT/ or ENABLE, are considered to be valid or

operative.

MIC2007YML датащи(PDF) 21 Page - Micrel Semiconductor

MIC2007YML датащи(HTML) 21 Page - Micrel Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

датащи скачать

ссылки URL